A Scrum transformation, just like any other change, is difficult and often unsuccessful. Large-scale culture shifts can be challenging for many reasons, but the length of time it takes to see significant results is usually a primary issue. Your company’s culture didn’t become what it is overnight, therefore it would be unreasonable to expect it to change overnight.
Make sure your leadership knows there will be a short term hit to productivity and output as the team learns the process. Additionally, try to communicate that it takes about a year for a team to become truly productive with Scrum, and around three years to achieve hyperproductivity. You will be investing lots of time, and patience is the essential factor that allows your investment to pay off.